1. Field of the Invention
The present invention relates to an imaging apparatus and imaging method capable of exposure control so as to give appropriate exposure, even in a case where aperture value has changed at the time of movie shooting and at the time of live view display.
2. Description of the Related Art
With an imaging device such as a camera, when driving an aperture at the time of movie shooting or at the time of live view display an appropriate exposure amount is maintained by simultaneously adjusting electronic shutter speed and ISO sensitivity. However, whereas there is delay in movement due to the fact that an aperture is driven mechanically, since electronic shutter speed and ISO sensitivity are electrically controlled there is almost no time lag in an operation of changing these values. As a result a time difference arises until an exposure it is desired to set is reached, and flicker arises in images for a movie or live view display, resulting in a visually undesirable screen.
An imaging apparatus has therefore been proposed that calculates a predicted value for current aperture position from aperture drive speed and target value, and electronic shutter speed and ISO sensitivity are set in order to operate in accordance with an aperture value that has been predicted (refer, for example, to Japanese patent laid-open No. 2013-031010 (hereafter referred to as “patent publication 1”)).
Also, an interchangeable lens, with which aperture value (FNo) is changed in accordance with change in focal length due to a zoom operation, in a state where aperture opening diameter is fixed, is generally used. With this type of interchangeable lens, focal length information in accordance with a zoom operation is transmitted to the camera body, and aperture control commands are transmitted from the camera body to the interchangeable lens so as to fix the aperture value (FNo). In this case, the interchangeable lens performs control to keep the aperture value (FNo) fixed by varying opening diameter in accordance with aperture control commands (refer, for example, to Japanese patent laid-open No. Hei. 11-183778 (hereafter referred to as “patent publication 2”)).
With patent publication 1 described above, electronic shutter speed and ISO sensitivity are controlled based on a predicted value for aperture value, which means that exposure fluctuation is suppressed and it is possible to alleviate image flicker. However, it is difficult to get a predicted value and actual aperture value to coincide completely, and as a result exposure fluctuations will arise at the time of movie shooting and at the time of live view display, causing image flicker. Also, in the case where a zoom operation is carried out during movie recording, if an aperture operation is carried out in order to keep the aperture value (FNo) fixed, there is a problem that flicker will arise in the image and image quality is lowered.